Metal artifacts of hip arthroplasty implants at 1.5-T and 3.0-T: a closer look into the B 1 effects
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TECHNICAL REPORT
Metal artifacts of hip arthroplasty implants at 1.5-T and 3.0-T: a closer look into the B1 effects Iman Khodarahmi 1 & John Kirsch 2 & Gregory Chang 1 & Jan Fritz 1 Received: 31 July 2020 / Revised: 27 August 2020 / Accepted: 30 August 2020 # ISS 2020
Abstract Objective To evaluate the effect of circular polarization (CP) and elliptical polarization (EP) of the B1 field on metal implantinduced artifacts of titanium (Ti) and cobalt-chromium (CoCr) hip arthroplasty implants at 1.5-T and 3.0-T field strengths. Material and methods In vitro Ti and CoCr total hip arthroplasty implants were evaluated using high transmit and receive bandwidth turbo spin echo (HBW-TSE) and slice encoding for metal artifact correction (SEMAC) metal artifact reduction techniques. Each technique was implemented at 1.5-T, which only allows for CP of B1 field as the system default, as well as 3.0-T, which permitted CP and EP. Manual segmentation quantified the size of the metal artifacts at the level of the acetabular cup, femoral neck, and femoral shaft. Results In the acetabular cup and femoral neck, 1.5-T CP achieved smaller artifact sizes than 3.0-T CP (28–29% on HBW-TSE, p = 0.002–0.005; 17–34% on SEMAC, p = 0.019–0.102) and 3.0-T EP (25–28% on HBW-TSE, p = 0.010–0.011; 14–36% on SEMAC, p = 0.058–0.135) techniques. In the femoral stem region, 3.0-T EP achieved more efficient artifact suppression than 3.0-T CP (HBW-TSE 44–45%, p < 0.001–0.022; SEMAC 76–104%, p < 0.001–0.022) and 1.5-T CP (HBW-TSE 76–96%, p < 0.001–0.003; SEMAC 138–173%, p = 0.003–0.005) techniques. Conclusion Despite slightly superior metal reduction ability of the 1.5-T in the region of the acetabular cup and prosthesis neck, 3.0-T MRI of hip arthroplasty implants using elliptically polarized RF pulses may overall be more effective in reducing metal artifacts than the current standard 1.5-T MRI techniques, which by default implements circularly polarized RF pulses. Keywords MRI . Hip arthroplasty . 3.0-T . Radiofrequency pulse . Polarization . Metal artifact
Introduction MRI is now recognized as the first- or second-line diagnostic test to evaluate patients with painful and dysfunctional hip arthroplasty, according to the American College of Radiology recommendations [1]. Patients with metal implants are often imaged at static magnetic field (B0) strengths of 1.5T and below, which is based on the physics principle that susceptibility artifacts are near-linearly proportional to B0 and, therefore, are more extensive at higher field strengths, such as 3.0-T. However, this practice may underrecognize
* Jan Fritz [email protected] 1
Department of Radiology, New York University Grossman School of Medicine, 660 1st Ave, 3rd Floor, New York, NY 10016, USA
2
Department of Radiology, Massachusetts General Hospital, Boston, MA, USA
beneficial effects arising from the B1 field polarization versatility at 3.0-T. MRI at higher field strengths benefits from increased signal-to-noise ratios, which can be traded for higher spatial or temporal resolutions to
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